593 research outputs found
NLO Corrections to Deeply-Virtual Compton Scattering
We have calculated the NLO corrections to the twist-2 part of the
deeply-virtual Compton scattering amplitude. Our results for the transverse and
antisymmetric parts agree with recent calculations by Ji and Osborne and by
Belitsky and M\"uller. In addition we present NLO results for the longitudinal
part of the amplitude.Comment: 8 pages, Latex. Error in polarised gluonic coefficient in Eq.(8)
correcte
Nuclear Shadowing and the Optics of Hadronic Fluctuations
A coordinate space description of shadowing in deep-inelastic lepton-nucleus
scattering is presented. The picture in the laboratory frame is that of
quark-gluon fluctuations of the high-energy virtual photon, propagating
coherently over large light-cone distances in the nuclear medium. We discuss
the detailed dependence of the coherence effects on the invariant mass of the
fluctuation. We comment on the issue of possible saturation in the shadowing
effects at very small Bjorken-.Comment: 11 pages, 5 figure
Linked Data Publication of Live Music Archives and Analyses
date-added: 2017-12-22 15:39:21 +0000 date-modified: 2017-12-22 15:53:18 +0000 keywords: Linked Data, Semantic Audio, Semantic Web, live music archive local-url: https://link.springer.com/chapter/10.1007/978-3-319-68204-4_3 bdsk-url-1: https://iswc2017.semanticweb.org/wp-content/uploads/papers/MainProceedings/221.pdf bdsk-url-2: https://dx.doi.org/10.1007/978-3-319-68204-4_3date-added: 2017-12-22 15:39:21 +0000 date-modified: 2017-12-22 15:53:18 +0000 keywords: Linked Data, Semantic Audio, Semantic Web, live music archive local-url: https://link.springer.com/chapter/10.1007/978-3-319-68204-4_3 bdsk-url-1: https://iswc2017.semanticweb.org/wp-content/uploads/papers/MainProceedings/221.pdf bdsk-url-2: https://dx.doi.org/10.1007/978-3-319-68204-4_3We describe the publication of a linked data set exposing metadata from the Internet Archive Live Music Archive along with detailed feature analysis data of the audio files contained in the archive. The collection is linked to existing musical and geographical resources allowing for the extraction of useful or nteresting subsets of data using additional metadata. The collection is published using a âlayeredâ approach, aggregating the original information with links and specialised analyses, and forms a valuable resource for those investigating or developing audio analysis tools and workflows
Molecular evolution of the hyaluronan synthase 2 gene in mammals: implications for adaptations to the subterranean niche and cancer resistance
The naked mole-rat (NMR) Heterocephalus glaber is a unique and fascinating mammal exhibiting many unusual adaptations to a subterranean lifestyle. The recent discovery of their resistance to cancer and exceptional longevity has opened up new and important avenues of research. Part of this resistance to cancer has been attributed to the fact that NMRs produce a modified form of hyaluronanâa key constituent of the extracellular matrixâthat is thought to confer increased elasticity of the skin as an adaptation for living in narrow tunnels. This so-called high molecular mass hyaluronan (HMM-HA) stems from two apparently unique substitutions in the hyaluronan synthase 2 enzyme (HAS2). To test whether other subterranean mammals with similar selection pressures also show molecular adaptation in their HAS2 gene, we sequenced the HAS2 gene for 11 subterranean mammals and closely related species, and combined these with data from 57 other mammals. Comparative screening revealed that one of the two putatively important HAS2 substitutions in the NMR predicted to have a significant effect on hyaluronan synthase function was uniquely shared by all African mole-rats. Interestingly, we also identified multiple other amino acid substitutions in key domains of the HAS2 molecule, although the biological consequences of these for hyaluronan synthesis remain to be determined. Despite these results, we found evidence of strong purifying selection acting on the HAS2 gene across all mammals, and the NMR remains unique in its particular HAS2 sequence. Our results indicate that more work is needed to determine whether the apparent cancer resistance seen in NMR is shared by other members of the African mole-rat clade.National Research Foundation (South Africa
Nonperturbative versus perturbative effects in generalized parton distributions
Generalized parton distributions (GPDs) are studied at the hadronic
(nonperturbative) scale within different assumptions based on a relativistic
constituent quark model. In particular, by means of a meson-cloud model we
investigate the role of nonperturbative antiquark degrees of freedom and the
valence quark contribution. A QCD evolution of the obtained GPDs is used to add
perturbative effects and to investigate the GPDs' sensitivity to the
nonperturbative ingredients of the calculation at larger (experimental) scale.Comment: 17 pages, 10 figures; submitted to Phys. Rev.
Gluon Polarization from QCD Sum Rules
The gluon polarization in a nucleon can be defined in a gauge
invariant way as the integral over the Ioffe-time distribution of polarized
gluons. We argue that for sufficiently regular polarized gluon distributions
is dominated by contributions from small and moderate values of the
Ioffe-time z < 10. As a consequence can be estimated with 20%
accuracy from the first two even moments of the polarized gluon distribution,
and its behavior at small values of Bjorken x or, equivalently, at large
Ioffe-times z. We employ this idea and compute the first two moments of the
polarized gluon distribution within the framework of QCD sum rules. Combined
with the color coherence hypothesis we obtain an upper limit for at a typical scale .Comment: 12 pages, Latex, 2 figures include
Inkjet printed LED based pH chemical sensor for gas sensing
Predictable behaviour is a critical factor when developing a sensor for potential deployment within a wireless sensor network (WSN). The work presented here details the fabrication and performance of an optical chemical sensor for gaseous acetic acid analysis, which was constructed using inkjet printed deposition of a colorimetric chemical sensor. The chemical sensor comprised a pH indicator dye (bromophenol blue), phase transfer salt tetrahexylammonium bromide and polymer ethyl cellulose dissolved in 1-butanol. A paired emitter-detector diode (PEDD) optical detector was employed to monitor responses of the colorimetric chemical sensor as it exhibits good sensitivity, low power consumption, is low cost, accurate and has excellent signal to noise ratios. The chemical sensor formulation was printed directly onto the surface the emitter LED, and the resulting chemical sensors characterised with respect to their layer thickness, response time and recovery time. The fabrication reproducibility of inkjet printed chemical sensors in comparison to drop casted chemical sensors was investigated. Colorimetric chemical sensors produced by inkjet printing, exhibited an improved reproducibility for the detection of gaseous acetic acid with a relative standard deviation of 5.5 % in comparison to 68.0 % calculated for drop casted sensors (n = 10). The stability of the chemical sensor was also investigated through both intra and inter-day studies
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